Implementation Diary - 6 March 2009

I am still struggling with Logistics Domain. As the closeness to finishing the goal reduces, the amount of effort needed increases. I played with several parameters in the past 1-2 days - distances between various objects, weights for selection of action, weightage given to conditions violated versus the fulfilment of cost while adding an action, and so on.

I have been unable to make many conclusive observations. Till now I have been able to obtain "3 non-zero costs" (previously I got to "2 non-zero costs" as well, but now seem to have lost it). These three costs are due to some conditions on locations of package_4 and package_6 - these packages have to be shipped from one city to another. I still have to find why these costs never get satisfied. However I have realized that since we gave a 1/d^3 weight to actions, tuning the distances used in cost computation play an important role. Finding appropriate weights needs research. Right now all of this seems so murky and having no correct answer.

I performed a little experiment with the 1/d^3 weight to actions: replaced 3 with e=.5, 0.75, 1, 1.5, 2 etc. Contrary to what I thought, e < 1 didn't work well at all. Best value was achieved near e = 1.5. This experiment does not mean much though and I would hate to bet anything on it.

During the day I also ran the cost performance profile tool. It generates a graph for "number of non-zero costs" with a large number of ups and downs:

Putting filters on selection of action instances (like do not select actions that lead to more cost value on the cost being fixed) reduce the number of times "3 non-zero costs" is achieved.